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  • Title: The K+-channel opener NS1619 increases endothelial NO-synthesis involving p42/p44 MAP-kinase.
    Author: Kuhlmann CR, Trümper JR, Abdallah Y, Wiebke Lüdders D, Schaefer CA, Most AK, Backenköhler U, Neumann T, Walther S, Piper HM, Tillmanns H, Erdogan A.
    Journal: Thromb Haemost; 2004 Nov; 92(5):1099-107. PubMed ID: 15543339.
    Abstract:
    Ca(2+)-activated K(+) channels with large conductance (BK(Ca)) have been shown to play an important role in the regulation of vascular tone. We examined the role of the p42/p44 MAP-kinase (p42/p44(MAPK)) on nitric oxide (NO) production in human endothelial cells induced by the BK(Ca)-opener NS1619. Using DiBAC-fluorescence imaging a concentration-dependent (2.5-12.5 microM) hyperpolarization induced by NS1619 was observed. A significant increase of intracellular Ca(2+)-concentration by NS1619 was seen using Fura-2-fluorescence-imaging, which was blocked by 2-APB, or reduction of extracellular Ca(2+) (n=30; p<0.05). A cGMP-radioimmunoassay was used to examine NO synthesis. NS1619 significantly increased cGMP levels which was inhibited by LNMMA, iberiotoxin, BAPTA, 2-APB, reduction of extracellular Ca(2+), PD 98059, or U0126 (cGMP (pmol/mg protein): NS1619 3.25 +/- 0.85; NS1619 + L-NMMA 0.86 +/- 0.02; NS1619 + iberiotoxin 0.99 +/- 0.09; NS1619 + BAPTA 0.93 +/- 0.29; NS1619 + 2-APB 0.99 +/- 0.31; NS1619 + Ca(2+)-reduction 1.17 +/- 0.06; NS1619 + PD98059 1.06 +/- 0.49; NS1619 + U0126 1.10 +/- 0.24; n=10; p<0.05). The phosphorylation of eNOS and p42/p44(MAPK) was examined by immunocytochemistry. Phosphorylation of p42/p44(MAPK) was significantly increased after 10 minutes of NS1619 stimulation, whereas eNOS phosphorylation was not changed over a period of 1 to 30 minutes. NS1619-induced hyperpolarization was not affected by treatment with PD 98059 or U0126. Additionally, NS1619 inhibited endothelial proliferation involving a NO-dependent mechanism. Our data demonstrate that NS1619 causes a transmembrane Ca(2+)-influx leading to an increased NO production involving p42/p44(MAPK). This rise of NO formation is responsible for the NS1619 induced reduction of endothelial cell growth.
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